I found this post in a ASU corvette site while i was assigned in Arkansas and saved it....i have posted it as i found it
I put an 89 700R4 in my 71 and it's a wonderful addition
for the street, I'm getting 19 mpg at 70 to
80 mph cruise with a 406/375, much better than the 14 to 15
or so that I got with the TH400. The 700R4 is
also lighter and takes some 30HP less to turn than a
TH-400.
http://www.bowtieoverdrives.com...has crossmembers, driveshafts, shifter kits, correct
carb throttle shaft brackets, TV Cable brackets,
and transmissions available for swaps now (they didn’t
exist in 1992 when I performed this swap).
Your Bellhousing and flexplate to converter bolt pattern
will be no problem,the V8 700's come in a Chevy
bellhousing only. You can use the 700's converter cover or
mod your old one with some tin snips and a drill.
Your cooler lines should work with a little bending.
You'll need12 volts down there if you retain the "torque
converter clutch". You should retain the lock-up if
your cruise rpm in OD is anywhere around the converter's
stall speed, also the TTC is worth about 1.5 mpg to ya,
though it depends on your rear gear and rear tire size. My
700 is setup to lock up in fourth only, and all I had to do was supply 12 volts (which was already there from the TH400), other people do it differently so talk to your tranny builder about it.
If using a stock tranny from the wrecker talk to BM or TCI
as they have some stuff to set up a stock 700.
You'll have to bend the 700's dipstick tube a little bit
but it will fit.
You'll need to balance and shorten the driveshaft approx
3.5" if coming from a TH-400, not sure about TH-350 (it’ll be pretty close), it might work but in either case measure in the car!
You have two options with the rear mount, the 700R4 has two
different mounting provisions, a mount on
the case that's 22.75" from the engine mounting surface),
and an optional tailhousing mount that's 27.75"
from the engine mounting surface.
If coming from a TH350 you probably have a plate that's
bolted to the crossmember and the tranny mounts to
that (like the 4 speeds), you could maybe drill new holes
in the plate and mount the 700R4 to it with the
case mount if the height (pinion angle) works out, OR, you
could remove the above plate and drill new holes
in the crossmember itself and use the 700's optional
tailhousing mount (that's what I did coming from a
TH400, and that's how GM did it in 82) and mount to the
crossmember,
If you’re coming from an TH350 you should already have the
small diameter driveshaft which means that
if you want to retain the handbrake it will be easier for
you than it was for me,
If you want to retain the handbrake you'll have to remove
and reweld the handbrake cable pulley a little bit over towards the driver's side on the crossmember so the handbrake cable clears the yoke, and speaking of yokes, the smaller the better. I ended up using a yoke from a late 60's 4 speed,
the kind with U bolts instead of caps (L88's came with
them so they're strong). The reason is that since the tranny is longer the yoke is closer to the rear of the driveshaft tunnel, right where it starts to get thinner, if the handbrake is not an
issue any yoke will work, assuming reasonable body to frame
alignment, something those of us with old Vettes shouldn't assume.
If you have a single exhaust crossmember, you could perhaps
bolt in a 82 crossmember which I "think" has the handbrake pulley already moved.
Your stock shifter will work but you will have to modify
the shifter cable's bracket at the tranny's end to
make the bolt holes line up, one hole will be fine and the
other no good, so I welded on a tab and drilled a new
hole, a proper 700 bracket might work, not sure.
Your stock shifter will not allow first gear to be held,
you'll get 2, 3, and D (same as the 82's), if you
want first gear too you'll have to grind an extra detent
into the shifter's detent plate, there is plenty of
travel, OR, Ecklers now sells a kit with a shifter gate and
cable bracket etc for the swap, $80 or so.
The 700R4 doesn't have a vacuum modulator so that vacuum
line as well as the kickdown cable can go
away, make sure to plug the vacuum line.
The 700R4 uses a TV cable to control part-throttle
shiftpoints, line pressure, and kickdown. As this cable controls line pressure it's critical to the tranny's health and well
being that it's adjusted correctly. You'll need the proper
"TV Cable Bracket" that works with a Q-Jet, and it'll
probably have to modified to clear the powerbrake
vacuum line, I cut mine in half and welded a retaining pin
on it so it would work being held by only one bolt.
You'll need a little ball end to mount the cable to your
carb linkage, I cut the factory cable end off and used a
generic cable stop with a setscrew instead of fooling with
the factory adjuster.
Note: Bowtie OD's has a proper throttle linkage bracket for
correctly mounting the TV Cable to the carb.
If you have the ignition to shifter interlock (trans is
locked in park with the key off and removed), you'll
probably have to disable that as the cable will be too
short, just wire it open on the steering column.
The speedo cable will most likely work (mine did but
barely), but might be too short. If so a speedo shop can
make an extension if needed. Make sure your tranny is setup
for the mechanical speedo as 700's came with
electrical speedos too. You might have to mess with the
speedo drive's gearing to match your rear gear and
tire size, talk to your builder.
The 700R4 was constantly updated and the best ones are late
87 to 92 as they incorporate all the factory
upgrades. Earlier ones can be retrofitted with most but not
all of the upgrades, but it's expensive hard parts
we're talking about here. The late 87 to 92's can be
recognized by the lack of pressure ports on the case.
The Vette, Iroc, Trans Am and Z-28 700's came with the best
valvebody that allows a full throttle upshift to
fourth, better servo etc. The lesser trannies won't do it
unless the valvebody is modified, which takes a "real expert" and not just that B&M gizmo!
Also, the 84 and up VETTE trans has a shorter output shaft
and a funny tailhousing. I don't think you can use
it with the standard type tailhousings because of the
length of the output shaft. If you're going to the wrecker
best to use the IROC (Z-28) or Trans Am version and change
the tailhousing to which ever you need.
Don't confuse with 4L60E (93 up), which has no TV cable and
needs a computer to run.
Also don't confuse with a V6 model which has a much smaller
bellhousing and very different mounting surface.
They tend to run hot so an external cooler is a "GREAT"
idea, and if your doing any type of racing it's manditory!
As far as factory converters go there are two options, 1400
stall stock, and a 2000 stall Vette, Iroc, Trans
Am etc. They both have the clutch, but the aftermarket can
supply anything you want with or without a clutch.
If your engine is stock a stock 700 hi po should be fine,
though if you've got a hot motor then you'll need a
custom build to handle the torque,
Factory standard 700's are rated for 325 ft/lbs,
Factory hi po for 375 ft/lbs,
Aftermarket builds from 450 to 500 ft/lbs.
I got mine from Mike Bastio at Toy Shop Transmissions in
LA, (909) 620-5849,
(475 ft/lbs)
A friend of mine has had good luck with one from Premier
Performance in LA,
(714)630-3235,
(450 ft/lbs)
Art Carr builds the strongest full race ones for the
biggest $$$’s (500 ft/lbs).
TCI and B&M (450 ft/lbs) are expensive, (they charge big
money for every bracket and cable etc, instead of
including the little stuff), also BM cannot supply the tail
housing with the mount if that's how you end up
going (you can get it from a wrecker or GM, but it's more
$$$’s).
Keep in mind that they are not as strong as TH-400's, as a
VN'er with a over 500 ft/lbs Lingenfelter stroker found out the hard way recently.
If you see that kind of power in your future consider a
4L80E, much more money, much bigger and harder to install (possibly modify floor pan etc), much heavier, AND much stronger!
As all cars are different, weight and gearing etc, be
prepared to spend time messing with the governor
springs and weights to dial your full throttle shift
points, and the TV cable adjustment to dial your part
throttle shiftpoints and firmness.
Also, if your on the edge of detonation with your motor
now, you'll have to mess with your timing curve
because you'll be able to apply much more low rpm load to
your motor in OD than you could with your three
speed tranny.
The 700's ratios are,
1) 3.06
2) 1.62
3) 1.00
4) 0.70
Another thing to consider is that these trannys were
designed to be run with 3.08 or 3.23 rear gear ratios
(factory performance ratios) and 26" to 25.5" diameter
tires, I would guess that 3.36 or 3.55 would be ok
with 27" diameter tires (stock C3 255/60/15 or 225/70/15).
If you run with 3.70 rear gears or above you might not be
able to launch as well at the drags without slicks (because
of that 3.06 first gear), but that's depending on
your power level of course.
But hey, it's all worth it! I have a 3.08 in mine with
25.5" diameter tires and I cruise on the freeway around 2000 rpm getting around 19 mpg (with a
carbed 400ci), plus it's really quiet even with headers and
turbo mufflers!.
The 1.62 second gear is an awsome passing gear, it'll top
150 mph I figure (haven't tried that yet, but I have seen 135 mph at about
2/3 throttle which was at the tire's limit), and it has run a 12.87@112 at the strip.
Hope this helps, let me know how it goes,
Doug
71Coupe...406/375...700R4/F41
91 Coupe...350/250...ZF6/Z07
Questions contact Doug at
djdayson@ATTBI.COM______________
|IMG|https://www.c3vr.com/member_uploads/1301_1400/1333/br80.jpg |/IMG|
